1. Field of the Invention
The present invention relates to an inverter device, a display device, and a method of monitoring the display device and more particularly to an inverter device, a liquid crystal display device using an inverter, and method of monitoring lamps of a liquid crystal display device using the inverter device.
2. Description of the Related Art
In general, liquid crystal display (LCD) devices control light transmittance that is supplied from a backlight device to a liquid crystal display panel device to display image date (i.e., a picture) on a display screen. The liquid crystal display panel device includes a plurality of liquid crystal cells arranged in a matrix configuration and a plurality of control switches to switch video signals supplied to each of the liquid crystal cells. Since LCD devices can be made relatively smaller that cathode ray tube (CRT) devices, LCD devices are commonly used in laptop and desktop computers, photocopying machines, mobile telephones, and personal digital assistant (PDA) devices. The LCD devices require a backlight device used as a light source and optical sheets to reduce light loss generated in the backlight device.
The LCD device can be classified into direct-type backlight devices and edge-type backlight devices. The direct-type backlight devices include fluorescent lamps that are positioned to provide uniform light across an entire back surface of a display panel using a diffusion plate. The edge-type backlight devices include fluorescent lamps that are positioned to provide light incident to the display panel through a light guide panel, and are fastened to a side surface of the light guide panel to uniformly disperse light throughout the light guide panel and are surrounded by a lamp housing. The lamp housing supports the fluorescent lamps and prevents the light generated by the fluorescent lamp from leaking to side surfaces of the lamp housing. The diffusion plate is disposed between the display panel and top surfaces of the light guide panel, wherein the display panel includes a lower substrate where thin film transistors and pixel electrodes are arranged, an upper substrate where a color filter is formed, and liquid crystal material layer disposed between the lower and upper substrates. A reflective plate is included to prevent light from leaking onto a lower portion of the light guide panel. Cold cathode fluorescent lamps (CCFLs) or halogen cathode fluorescent lamps (HCFLs) can be used as the fluorescent lamps.
FIG. 1 is perspective view of a backlight device having an HHL-type arrangement of backlight lamps according to the related art. In FIG. 1, a first backlight lamp 10 is electrically connected to a second backlight lamp 12, wherein a low side of each of the first and second backlight lamps 10 and 12 are electrically interconnected to a low power source, and a high side of each of the first and second backlight lamps 10 and 12 are separately connected to a high power source. Accordingly, current flow is through both of the first and second backlight lamps 10 and 12. Thus, if one of the first and second backlight lamps 10 and 12 stops producing light (i.e., stops working), both lamps will stop producing light.
FIG. 2 is a perspective view of a backlight device having an HLHLHL-type arrangement of backlight lamps according to the related art. In FIG. 2, a first backlight lamp 10, a second backlight lamp 12, and a third backlight lamp 14 are each separately connected between high and low power sources. Accordingly, if one of the first, second, and third backlight lamps 10, 12, and 14 stops working, the other ones of the first, second, and third backlight lamps 10, 12, and 14 keeps producing light.
FIG. 3 is a perspective view of a backlight device having an HHHL-type arrangement of backlight lamps according to the related art. In FIG. 3, a first backlight lamp 10, a second backlight lamp 12, and a third backlight lamp 14 have a first end electrically interconnected to a low power source. In addition, each of the a first backlight lamp 10, a second backlight lamp 12, and a third backlight lamp 14 have a second end separately connected to a high power source. Accordingly, if one of the first, second, and third backlight lamps 10, 12, and 14 stops working, the other ones of the first, second, and third backlight lamps 10, 12, and 14 stop producing light. Moreover, it may not be possible to exactly control the current loss generated in an output line or light provided to the reflective plate.
FIG. 4 is a perspective view of currents flow within each of the HHL-type arrangement of backlight lamps according to the related art. In FIG. 4, since the current flowing through the first, second, and third backlight lamps 10, 12, and 14 is the same, it is not possible to exactly control the current loss generated in an output line or the amount light provided to the reflective plate. For example, a current of 6.85 mA flows through the first backlight lamp 10, a current of 8.2 mA flows through the second backlight lamp 12, and a current of 7.2 mA flows through the third backlight lamp 14. Accordingly, since a loss occurs in the output line and the lamp housing and the reflective plate cannot be controlled, it is not possible to make the same current flow through each of the first, second, and third backlight lamps 10, 12, and 14. Thus, characteristics of the first, second, and third backlight lamps 10, 12, and 14 cannot be checked since the amount of current flowing through the first, second, and third backlight lamps 10, 12, and 14 are different.